It has been disclosed that a cyclopropane carboxylic acid ester of a fluorinated benzyl alcohol having the general formula: ##STR1## wherein a and b independently represent 1, 2, 3, or 4 and c represents 0, 1, or 2 has a high insecticidal activity (DE-A-2658074 etc.). In particular, it has been disclosed that a cyclopropane carboxylic acid ester of 2,3,5,6-tetrafluorobenzyl alcohol has a high insecticidal activity and that it has a lower toxicity to mammals compared with a cyclopropane carboxylic acid ester of pentafluorobenzyl alcohol, and therefore, is a superior insecticide (DE-A-3705224).
As a process for producing the fluorinated benzyl alcohol having the general formula (I), a process has been proposed of reducing a halogen substituted benzoic acid derivative with a metal hydrides such as NaBH.sub.4, LiAlH.sub.4. For example, DE-A-3714602 discloses a process for producing 2,3,5,6-tetrafluorobenzyl alcohol by reacting 2,3,5,6-tetrafluorobenzoic acid with NaBH.sub.4 followed by treating with an alkylation agent. Further, DE-A-2658074, 2714042, and 2661074 disclose processes for producing for reducing polyfluorobenzoyl fluoride with NaBH.sub.4 to produce polyfluorobenzyl alcohol and processes for reducing polyfluorobenzoyl fluoride with LiAlH.sub.4 to produce a polyfluorobenzyl alcohol wherein one or more fluorine substituted groups are defluorinated. EP-A-31199 discloses a process for reacting 1,2,4,5-tetrafluorobenzene and n-butyl lithium and then reacting with carbon dioxide to form 2,3,5,6-tetrafluorobenzoic acid, which is reduced with LiAlH.sub.4 to produce 2,3,5,6-tetrafluorobenzyl alcohol.
On the other hand, electrolytic reduction processes have also been proposed as processes for the production of a fluorinated benzyl alcohol having the general formula (I). For example, JP-A-1-119686 discloses a process for the production of 2,3,5,6-tetrafluorobenzaldehyde and 2,3,5,6-tetrafluorobenzyl alcohol by electrolytic reduction of pentafluorobenzoic acid using a solid metal or a solid alloy as a cathode and an aqueous solution of sulfuric acid, hydrochloric acid, phosphoric acid, or sulfonic acid as an electrolyte. Further, JP-A-63-206491 discloses production of 2,3,5,6-tetrafluorobenzyl alcohol as a mixture with pentafluorobenzyl alcohol so as to electrolytically reduce pentafluorobenzoic acid using a solid metal or solid alloy as a cathode and an aqueous sulfuric acid solution as an electrolyte. There are many reports on processes for production of a fluorinated benzyl alcohol by electrolytic reduction, but in the same way as above, a benzyl alcohol is produced as a mixture in each case ("J. Electroanal. Chem.", 1991, p. 215; "J. Electroanal. Chem.", 1987, p. 315; "J. Chem. Soc. Perkin Trans I", 1972, p. 189; "J. Appl. Electrochem.", 1992, p. 1082; "Denkikagaku oyobi Kogyobutsurikagaku", 1990, p. 83; etc.)